This application relates to a relief valve for a pressurized container, and specifically to a relief valve including a frangible member rupturable in response to predetermined pressure and having modification prevention features.
Typically, a pressurized container or cylinder is filled with a gas or a liquid gas mixture under a predetermined pressure. Each container is designed and built to withstand a predetermined pressure under a standard set of conditions. Accordingly, a relief valve is included with the container that opens when pressure increases above the predetermined pressure. The relief valve prevents over pressurization and thereby failure of the container. Increases in pressure within the container results from overfilling or from exposure to a heat source. In each instance, the relief valve opens a passageway to release gas from the container and prevent bursting.
Some users incorrectly equate added pressure with added power, speed, etc. . . . and purposefully attempt to over pressurize the container. The standard relief valve will prevent this unless tampered with and modified to allow over pressurization. Tampering with a relief valve to allow over pressurization of a pressurized container or cylinder used by consumers, such as for paint ball guns, can result in injury. For this reason, known relief valves are constructed such that after bursting a new relief valve is required.
However, some users modify the relief valve to allow increased pressure within a gas cylinder. The modified relief valve allows the gas pressure within the gas cylinder to be increased substantially beyond the rated or predetermined pressure. This presents a very dangerous condition for the user. It is therefore desirable to design a relief valve that is tamper proof and tamper evident such that any unauthorized modification of the relief valve can be detected to evidence misuse by the user and render the relief valve inoperable to prevent use of the pressurized container.
Typically, relief valves are constructed as a threaded member installed into the gas cylinder or components assembled thereon. The relief valve includes a frangible member that will open the interior of the gas cylinder to atmosphere upon bursting.
Typically, the frangible member is fabricated from a frangible material such as copper. The thickness of the material corresponds to a pressure at which the relief valve is to open. As appreciated, the area exposed to gas at a pressure, and the thickness of the frangible member act in concert to determine the relief pressure for a specific gas cylinder. If the pressure within the gas cylinder increases beyond the relief pressure, the frangible member will rupture and allow gas to escape to atmosphere.
Tampering with or changing the dimensions of the frangible member will change the amount of pressure required to blow the relief valve. It is known to crimp a frangible member to a threaded member to prevent and evidence unauthorized modification of the relief valve. However, often times crimping of the frangible member is not sufficient to prevent removal with simple tools.
Accordingly, it is therefore desirable to develop a relief valve that prevents tampering, and will evidence attempts at modification.